Need someone to convert .mp video files

I have some .mp format video file so you have to help me play into my pc and also show me how you converted it. These videos are encrypted with some serial key in a software and i have lost that serial key so you have to solve my this issue by making it playable in all video player or by going passthrough that software which needs that serial key.

The below video explains how the system works if you have a serrial key: